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10. Appendix C: Default Configuration
The configuration described below corresponds to the LUFP7 gateway’s default configuration.
This chapter mainly gives the user information about the performances obtained on the
downstream Modbus network. It allows the user to decide whether, for example, he should
change the period for cyclical exchanges with one or more of the TeSys U motor starters (see
chapter 6 Configuring the Gateway, page 44).
10.1. Configuring Modbus Exchanges
The LUFP7 gateway carries out four types of exchanges with each of the 8 TeSys U motor starters. The first two
exchanges are cyclical and allow you to control and monitor the motor starter. The last two exchanges are
aperiodic (only when there is a change in the values of the data to be transmitted to the motor starter) and allow
you to read and change the value of any motor starter parameter.
Function Modbus function
Number of
bytes (1)
Exchange between the LUFP7 gateway
and the TeSys U motor starter
16#03
Read Holding
Registers
11,5 + 10,5
Periodic reading (300 ms period) of the TeSys U motor
starter’s status register (address 455 = 16#01C7) only
16#10
Preset Multiple
Registers
14,5 + 11,5
Periodic writing (300 ms period) of the TeSys U motor
starter’s status register (address 704 = 16#02C0) only
(16#03)
(Read Holding
Register)
011,5 + 10,5
Aperiodic reading of the value of a single parameter, for a
single TeSys U motor starter at a time (function and
address supplied by the user)
(16#06)
(Preset Single
Register)
11,5 + 11,5
Aperiodic writing of the value of a single parameter, for a
single TeSys U motor starter at a time (function and
address and value supplied by the user)
(1) Number of bytes in the Query + number of bytes in the Response, plus a period of silence of 3.5 characters
for each of these two frames (see description of the “Message delimiter (10ms)” parameter in
chapter 6.12.3 “Sub-Network” Element, page 83). Each byte will be transmitted in the form of a group of
10 bits (8 data bits, 1 start bit and 1 stop bit). These values allow you to calculate the approximate amount
of traffic on the downstream Modbus network as follows:
Volume of periodic traffic (300 ms period).....................
[ (11.5 + 10.5) + (14.5 + 11.5) ] × (8 + 1 + 1) = 480 bits
For 1 TeSys U motor starter ............................................................... 1 × 480 × (1,000 ÷ 300) = 01,600 bits/s
For 8 TeSys U motor starters ........................................................... 8 × 480 × (1,000 ÷ 300) = 012,800 bits/s
As a result, on a network operating at 9,600 bits/s, you will need to considerably increase the cycle time for
all or part of the periodic Modbus commands. On the other hand, at a speed of 19,200 bits/s (default
speed), the available bandwidth is sufficient to allow proper communications, even in occasional degraded
mode (frames re-transmission), and to allow the use of aperiodic parameter reading/writing exchanges.